They have Zero proof of it which is why they have not released it.
If there were any pics of crash site or crash smoke/fire inside our J&K visible from Pak side the net would have been flooded with those pics.
Multiple foreign analysts have written that only confirmed dowing on that day was a MiG-21.
They will think that a jet engaging after burners to flee is a jet on fire.
There is no hilly terrain in that area.
Also we know that Abhinandan MiG-21 came from the direction of Rajauri so his description matches exactly with Abhinandan MiG-21.
He says he saw a plane crashing near Sher Makadi which is just 5 km from actual crash site of Abhinandan so he might have though that Abhinandan's falling plane came down in sher makadi.
Also he clearly mentions he saw ONE pilot ejecting whcih matches with Abhinandan MiG 21 description as Sukhois have two pilots
5 km from crash site vow... Can humans see that far and describe details like pilot ejecting and chute opening ..... Guess the answer
Farthest a human with perfect vision see under perfect condition is 2.5 km ..
Unless he had penetrating vision like those penetrating spice 2000